Abstract

Fluid film bearings have been extensively used in the industry because of their unbeatable durability and extremely low friction coefficient. Large bearings supporting shafts of huge and important rotating machines constitute a special group of fluid film bearings since the reliability of crucial systems, like for example electro-energetic system, rely on their trouble-free operation. Large thrust bearings, apart from enormous consequences of failures, can also be characterized by severe conditions of operation. Despite very low coefficient of friction, due to large diameters dissipation of energy in such bearings is noticeable. In the contemporary economy with ever growing demands for increased efficiency there is always a need for improving performance of the machines. Two main aspects of increasing the efficiency can be distinguished - one is literal - the machines have to be more efficient so the losses, including friction in the bearings, have to be minimized. Looking at the components of losses in fluid film bearings, one can notice that apart from unavoidable losses in the film, there are losses generated outside the film which can possibly be avoided or decreased by bearing modifications. Some other possibilities of decreasing energy losses in the fluid film bearings will also be discussed in the paper. Another aspect of increasing overall efficiency of the machines is decreasing their downtime and limiting the number and consequences of failures. Unfortunately in the hydrodynamic bearing there is a contradiction between energy efficiency and margin of safety, very well shown by the Striebeck curve. Therefore in order to allow more efficient, and in the same time more risky, bearing operation it is necessary to predict bearing performance using more accurate bearing models, but simultaneously it is also necessary to improve bearing diagnostic tools to be able to prevent their failures. This requires the development of measurement and diagnostic methods, as condition monitoring based only on direct temperature measurement proved to be ineffective in numerous cases. The idea of active bearings is probably one of the solutions combining both aspects of efficiency - they can be energy-efficient and reliable in the same time.

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